A long, fine article by author J. Lee Anderson about the musicians and
calliopes aboard American riverboats appears in the July, 1996, issue
of "The Mississippi Rag". (The issue is available for 27169 2.00 from
P.O. Box 19068, Minneapolis, MN 55419.)   Photographs of a calliope in
action clearly show 32 whistles arranged chromatically upon a hairpin
manifold.  Anderson notes, "the number of whistles on a calliope varied
from 13 or 15 to as many as 58 ... many of the most popular instruments
had 32."

Most intriguing is that the very first calliope had variable-pitch
whistles, and was played by a pinned cylinder -- what a noisy music
box!

A few quotes from the text:
- - - -
The calliope's inventor, a beekeeper from Worcester, Mass., named
Joshua C. Stoddard, had a flair for things mechanical and loved to
tinker. ... While experimenting with steam whistles, Stoddard
discovered how to vary the pitch [by altering the pressure]. ... He
improved on his notion of a steam-operated music box by varying the
shape of the pins pegged in a revolving cylinder to produce whole,
half, quarter, eighths and lesser notes.

The pins, in revolving, lifted valves which admitted just the proper
squirt of steam to each of the whistles, resulting in a hoarse-toned
mechanical melody.  Eventually, the calliope was played from a
brass-keyed, piano-like keyboard.

Stoddard patented his instrument in 1855, and soon formed the American
Steam Music Company.  In August 1856 one of their new calliopes was
installed on the side-wheel tugboat "Union", which toured New York
harbors giving a free concert.